Eye-protective ophthalmic glass



Patented Sept. 7, 1954 OFFICE William H. Ai'mistead, Corning, N. Y., assignor to Corning Glass Works, Corning, N. Y., a corporation of New York No Drawing. Application April 2'7, 1953, Serial No. 351,493

8 Claims.

This invention relates to neutral or gray-colored ophthalmic crown glasses having substan tial absorption for infrared and ultraviolet as well as visible radiations and having the optical and physical properties which characterize White spectacle crown and which have come to be accepted as a standard in the trade, whereby such glasses are particularly suitable for use in eyecorrective lenses. Such optical and physical properties, as is well known, include a refractive index of 1523:0001, an expansion coeificient of about 92 to 98 x10 per 0. (between and 300 C.), and a softening point between about 710 and 735 C. (By softening point is meant that temperature at which the viscosity of the glass is poises.)

Infrared and ultraviolet radiations are effectively absorbed by glasses containing FeO and Fe203 respectively, and these oxides are commonly utilized in glasses for these purposes. A glass containing both FeO and Fe203, melted under reducing conditions, has a greenish color which can be neutralized to gray by combination with the complementary purple color produced by M0 in glasses of the type K20.R0.Si02 where R. is a bivalent metal of the second periodic group. The color of such a neutral colored glass is difficult to control, however, because the greenish complement tends to vary objectionably in hue depending upon the extent of the reduction.

As described in my copending applications, Serial No. 351,491 and Serial No. 351,492, filed concurrently herewith, the inclusion of Ti02 in such a glass provides control of the hue of its greenish complement and thereby of the desired neutral color, as a result of which minor variations in the reducing conditions can be readily tolerated without the production of any deleterious effects.

Application Serial No. 351,492 specifically discloses such reduced neutral-colored glasses comprising essentially 50 to 75% Si02, 14 to 23% K and at least one glass-stabilizing oxide in the indicated proportion selected from the group consisting of up to ZnO and up to 20% B203, the total oxides of such group being 6 to and containing glass-coloring components consisting of Fe0 and F6203 totalling 0.3% to 4.5% computed as Fe2Os, 0.1% to 2% Ti02, and 0.02% to 0.50% M0, the ratio of the computed FezOs/NiO being 5/1 to 15/1, such essential constituents totalling at least 75%. Na2O and/or L120 can also be included as essential constituents in such reduced neutral-colored glasses provided that the NazO does not exceed 17%, the H20 does not exceed 4%, the total Na20 and Li2O is not over 17%, and the total alkali metal oxide content does not exceed 25%. Preferably the amount of K20 does not exceed 20% and the total alkali metal oxide also does not exceed 20%. When Na20 and/or Li20 are present, moreover, the K20 content can be as low as 8% provided that the total alkali metal oxide content is at least 14%. In addition, auxiliary glass-stabilizing oxides including up to 12% BeO, up to 15% MgO, up to 20% CaO but not over 20% of MgO-l-CaO, up to 25% SrO, up to 25% CdO, up to 25% BaO, up to 15% A1 03 and up to 10% Zr02 can optionally be present, either singly or in combination, within the indicated amounts provided that their total does not exceed 25%.

Such glasses provide desirable reduction of glare and are useful for various general ophthalmic purposes. I have also found, however, that the ZnO-containing glasses, by suitable control of their composition, can surprisingly be made to possess not only the desired neutral color but also the physical and optical properties characterizing standard ophthalmic crown; and this application is specifically directed to such ZnO-containing glasses.

These reduced neutral-colored ZnO-containing glasses comprise essentially 63% to S102, 8% to 19% K20, at least one alkali metal oxide in the indicated proportion selected from the group consisting of up to 10% N220 and up to 4% L120, the percentage of Na20 being at least 4% when only K20 and Na20 are present and the percentage of 'Li20 being at least 1% when only K20 and Li20 are present, the selected alkali metal oxide comprising L120 when the percentage of K20 is between 16 and 19%, the total alkali metal oxides being 15% to 22%, and 5% to 17% ZnO, and contain glass-coloring components consisting of FeO and F8203 totalling 0.3% to 4.5% computed as F8203, 0.1% to 2% Ti02, and 0.02% NiO, the ratio of the computed FezOs/NiO being 5/1 to 15/1, the essential constituents totalling at least While the present glasses preferably consist of the indicated essential oxides, other glass-stabilizing oxides may also be included in an aggregate amount up to 10%. For example, up to 5% A1203 may advantageously be present; up to 5% E203 or up to 8% of one or more of the bivalent metal oxides BeO, MgO, C'aO, SrO, CdO, and BaO, preferably either CaO or BaO, may also be included. If desired, 2102 may also be utilized in amounts up to 5%.

The following glass compositions calculated 3 4 from their respective batches to the oxide basis counteract the increasing bluish tendency due to in parts by weight will illustrate the invention. the FeO and thus to maintain the desired greenish (The amounts of the coloring oxide, NiO, being complement; and, when the proportionate less than 0.50, are expressed to two significant amount of FeO is decreased, the TiO2 content places; but such practice is without significance 5 should be correspondingly decreased to avoid the in expressing the major constituents. Since the yellowish tendency otherwise caused by F6203 compositions total approximately, if not exactly, and T102. 100 the amounts given for the various constit The total iron oxide content of the glass howents thereof can for practical purposes be called ever, should be maintained Within the limits set percent by weight.) 10 forth above, because an excess in the total FeO as 65.6 63.4 68.6 is 6 18 11 14 4 s 4 3 1 1o 6 9 e 2 2 2 5 .1 3

"if? "56 l 1.5 1 o 22 0.33 010 0.20

The values of the refractive index expansion and FezOs cau s t e ge ra Of the glass coefficient, and softening point of the above to appear too green while a deficiency causes it glasses are within the aforementioned ranges and, 25 to pp OO de Colo due to on s no while any one value such as the refractive index substantially c ged when the glass is may vary slightly according to the size of the pered, that is, heated nearly to its softening point melt or other controllable factors, adjustment a s nIy led ni mly hr h v r can readily be made and the desired value obhiliidled degrees C- tained by suitable minor alteration of the batch t an e s 0f 2 e 60101 of the glass or change in melting conditions. For example, tends too much towards amber and with a decomposition 1 which is adapted for m ltin in ficiency the color tends too much towards blue. tank furnaces has a refractive index of 1.523, an An x ss f 0 causes h color of the glass expansion coefficient of 96 10- per C., and a to app r too p p and a deficiency of N10 softening point of 728 C. causes the color to appear too green. The color To provide the desired greenish complementary due to NiO is fied by t mpering the glass; color of the iron oxides, the batches for the resq ly, if the glass is to be tempered, the

ent glasses are melted under reducing conditions, NiO content o l b l w r li tly. en r ll advantageously by introducing part of the iron 0n the Order o about oxide content into each batch as a ferrous com- It is essential that glass-coloring Oxide Other pound, for example as ferrous oxalate, or alterthan Fezoz, Ti02 and N10 be present in the natively by including in a batch containing FezOg glasses of this invention because the desired neua small amount of starch. Since the reducing trel c0 1 cann t Otherwise be obtained.

agent for example the oxalate radical or the e olor of the present ass is also instarch, is completely eliminated during melting fiuenced to some extent by the selection and/or of the batch, it is not included in th final combination of certain of the optional constitupositions given above. The proportion of oxalate ehtseXample, the p p Co p e nt f or starch or other reducing agent which produces the NiO t ds t be Shi ted Somewhat towards the desired result will vary with the glass comember y an increasing eOIlteht 0f BeO 0 O position and/or the particular melting condiand, to a less extent of (32.0 unless the total alkali I tions. Less reducing agent is required for meltmetal oxide content is near the maximum. On ing in a closed melting container or covered pot the Other hand, the p s o than for melting in an open melting container A1203, ZIOZ in e glass Within t e abovesuch as a tank. The exact amount of reducing stated limits has no substantial effect upon its agent for all conditions cannot therefore be 001011 3 tends to Strengthen t e Pu p 00 stated, but for each condition it can readily be plementdetermined by trial. It is preferable to utilize To m i in e desired p op s of he presferrous oxalate as the reducing agent because ent glasses including the refractive in ex, t erglasses made from batches containing it fine more mel expansion eeefiieient. and softening p readily than glasses made from batches conthe proportions o the remaining Constituents taining starch. sugar or carbon. should be kept within the above-stated ranges for Due to the fact that FeO is a stronger glassthe following ns: coloring oxide than F6203, the ratio of the total An x ss f SiOz re ul in a ten ncy for the iron oxides to N10 or the computed F8203/Ni0 rarefractive index of the glass to be undesirably 10W tio may, without change of the neutral color, vary while a deficiency of S102 results in the refractive between 5/1 and 15/1, depending upon the proindeX b g tOO highportionate amount of FeO relative to that of An excess in the total amount of alkali metal F6203 or the extent of reduction of the glass. To oxide leads to an undesirably high expansion 0 decrease the ratio within such limits requires an efiicient, but a deficiency causes too low an exp increase in the proportionate amount of FeO or a sion coeflicient and too high a softening point stronger reduction and to increase the ratio re- Ei er K20 or N zO i exc s c es too hi h an quires a decrease in the proportionate amount of expansion coefiicient. Too much Nazo or L120 FeO or a weaker reduction. When the proporlowers the softening point undesirably. The color tionate amount of FeO is thus increased, the T102 of the glass also appears too amber if K20 is less content should be correspondingly increased to than 8%.

An undesirably high refractive index results from an excess of ZnO or the other bivalent metal oxides mentioned above. An insuflicient amount of Z110 may cause the glass to appear too amber in color especially if it contains substantial Na20.

An excess of A1203 or Zr02 raises the softening point of the glass undesirably. An excess of B203, on the other hand, tends to lower the softening point undesirably. Excessive Zr02 also tends to raise the refractive index too much.

If desired, Pb may also be included in amounts up to about 3% but more than this amount should be avoided because it not only raises the refractive index too much but tends to be reduced to metallic lead.

An important advantage of the present glasses is their capability of being edged substantially as rapidly as ordinary ophthalmic crown glasses. As is known, an ophthalmic lens is customarily edged or finished to its final peripheral shape after its faces have been ground with loose abrasives and polished to specified curvatures. Edgegrinding of the lens is accomplished by contacting its edge with a rotating wet grinder composed of a bonded abrasive. Such a grinder of course normally cuts more slowly than loose abrasives, which cannot be utilized for edging without undesirably producing scratches on the polished faces of the lens. For reasons not known, however, the edging or" various prior neutral-colored ophthalmic lenses by the use of conventional edgegrinders is unusually slow and has been known to require up to ten times as long as that of ordinary ophthalmic crown lenses. No such difliculty is encountered with lenses made from the glasses of this invention.

As indicated above, glasses of the present type in which the essential glass-stabilizing oxide is either ZnO or B203 are broadly described and claimed in my aforementioned application Serial No. 351,492; and glasses of the present type in which the essential glass-stabilizing oxide is either BeO, MgO, CaO, Sr0, CdO, BaO, A1203 or Zr02 are broadly described in my aforementioned copending application Serial No. 351,492.

What is claimed is:

1. A reduced, substantially neutral-colored, infrared-absorbing and ultraviolet-absorbing glass having a refractive index (nD) of about 152310.001, an expansion coefficient of about 92 to 98 10' per C. and a softening point between about 710 and 735 0., and comprising essentially 63 to 70% S102, 8 to 19% K20, at least one alkali metal oxide in the indicated proportion selected from the group consisting of up to 10% 172120 and up to 4% L120, the percentage of Na20 being at least 4% when only K20 and Na20 are present and the percentage of L120 being at least 1 when only K20 and Li20 are present, the selected alkali metal oxide comprising L120 when the percentage of K20 is between 16 and 19%, the total alkali metal oxides being to 22%, and 5 to 17% ZnO, and containin glass-coloring components consisting of Fe0 and Fe202 totalling 0.3 to 4.5% computed as FezOz, 0.1 to 2% T102, and 0.02 to 0.50% N10, the ratio of the computed Fes/Ni0 being from 5/1 to 15/1, the essential constituents totalling at least 90%.

' 2. A reduced, substantially neutral-colored, infrared-absorbing and ultraviolet-absorbing glass having a refractive index (nD) of about 1523:0001, an expansion coefficient of about 92 to 98 l0 per C. and a softening point between about 710 and 735 0., and comprising essentially 63 to 70% S102, 8 to 19% K20, at least one alkali :metal .oxide in the indicated proportion selected from the group consisting of .up to 10% M220 and up to 4% L120, the percentage of NazO being at least 4% when only K20 and Na20 are present and the percentage of L120 being at least 1% when only K20 and L120 are present, the selected alkali metal oxide comprising L120 when the percentage of K20 is between 16 and 19%, the total alkali metal oxides being 15 to 22% and 5 to 17% ZnO, and containing glass-coloring componentsconsisting of FeO and Fezostotalling 0.3 to 4.5% computed as F6203, 0.1 to 2% T102 and 0.02 to 0.50% N10, the ratio of the computed Fe203/Ni0 being from 5/1 to 15/1, the essential constituents totalling at least and up to 5% A1203.

-3. A reduced, substantially neutral-colored, infrared-absorbing and ultraviolet-absorbing glass having a refractive index (11D) of about 152310.001, an expansion coeflicient of about 92 to 98 10 per C. and a softening point between about 710 and 735 0., and comprising essentially 63 to 70% S102, 8 to 19% K20, :at least one alkali metal oxide in the indicated proportion selected from the group consisting of up to 10% Na20 and up to 4% L120, the percentage of Na20 being at least 4% when only K20 and Na20 are present and the percentage of L being at least 1% when only K20 and Li20 are present, the selected alkali metal oxide comprising L120 when the percentage of K20 is between 16 and 19%, the total alkali metal oxides being 15 to 22%, and 5 to 17% 'ZnO, and containing glass-coloring components consisting of FeO and Fe203 totalling 0.3 to 4.5% computed as Fe203, 0.1 to 2% T102 and 0.02 to 0.50% N10, the ratio of the computed Fe203/Ni0 being from 5/1 to 15/1, the essential constituents totalling at least 90%, and up to 5% 13203.

4. A reduced, substantially neutral-colored, infrared-absorbing and ultraviolet-absorbing glass having a refractive index (72B) of about an expansion coefficient of about 92 to 98 10-' per C. and a softening point between about 710 and 735 0., and comprising essentially 63 to 70% S102, 8 to 19% K20, at least one alkali metal oxide in the indicated proportion selected from the group consisting of up to 10% Na2O and up to 4% L120, the percentage of Na20 being at least 4% when only K20 and Na20- are present and the percentage of L120 being at least 1% when only K20 and L120 are present, the selected alkali metal oxide comprising L120 when the percentage of K20 is between 16 and 19%, the total alkali metal oxides being 15 to 22%, and 5 to 17% ZnO, and containing glass-coloring components consisting of FeO and Fe203 totalling 0.3 to 4.5% computed as Fe203, 0.1 to 2% T102 and 0.02 to 0.50% N10, the ratio of the computed Fe203/Ni0 being from 5/1 to 15 1, the essential constituents totalling at least 90%, up to 5% A120: and up to 5% B203.

5. A reduced, substantially neutral-colored, inflared-absorbing and ultraviolet-absorbing glass having a refractive index (nD) of about an expansion coefiicient of about 92 to 98 10- per C. and a softening point between about 710 and 735 0., and comprising essentially 63 to 70% S102, 8 to 19% K20, at least one alkali metal oxide in the indicated proportion selected from the group consisting of up to 10% Na20 and. up

to 4% Li20, the percentage of Na20 being at least 4% when only K20 and Na2O are present and the percentage of Li20 being at least 1% when only K20 and Li20 are present, the selected alkali metal oxide comprising Li20 when the percentage of K20 is between 16 and 19%, the total alkali metal oxides being 15 to 22%, and 5 to 17% ZnO, and containing glass-coloring components consisting of Fe and Fe203 totalling 0.3 to 4.5% computed as Fe203, 0.1 to 2% T102 and 0.02 to 0.50% NiO, the ratio of the computed FezOs/NiO being from 5/1 to 15/1, the essential constituents totalling at least 90%, and up to 3% of at least one bivalent metal oxide selected from the group consisting of BeO, MgO, CaO, SrO, CdO and BaO.

6; A reduced, substantially neutral-colored, infrared-absorbing and ultraviolet-absorbing glass having a refractive index (nD) of about an expansion coeflicient of about 92 to 98 l0 per C. and a softening point between about 710 and 735 0., and comprising essentially 63 to 70% Si02, 8 to 19% K20, at least one alkali metal oxide in the indicated proportion selected from the group consisting of up to 10% N220 and up to 4% Li20, the percentage of Na2O being at least 4% when only K20 and Na20 are present and the percentage of Li20 being at least 1% when only K20 and Li2O are present, the selected alkali metal oxide comprising Li20 when the percentage of K20 is between 16 and 19%, the total alkali metal oxides being to 22%, and 5 to 17% ZnO, and containing glass-coloring components consisting of FeO and Fe203 totalling 0.3 to 4.5% computed as Fe202, 0.1 to 2% Ti02 and 0.02 to 0.50% NiO, the ratio of the computed Fe2O2/Ni0 being from 5/1 to 15/1, the essential constituents totalling at least 90%, up to 5% B203, and up to 8% of at least one bivalent metal oxide selected from the group consisting of BeO, MgO, CaO, SrO, CdO and BaO.

7. A reduced, substantially neutral-colored, infrared-absorbing and ultraviolet-absorbing glass having a refractive index (nD) of about an expansion coefficient of about 92 to 98 10-' per C. and a softening point between about 710 and 735 0., and comprising essentially 63 to Si02, 8 to 19% K20, at least one alkali metal oxide in the indicated proportion selected from the group consisting of up to 10% Na2O and up to 4% Li20, the percentage of Na20 being at least 4% when only K20 and Na20 are present and the percentage of Li20 being at least 1% when only K20 and Li20 are present, the selected alkali metal oxide comprising Li20 when the percentage of K20 is between 16 and 19%, the total alkali metal oxides being 15 to 22%, and 5 to 17% ZnO, and containing glass-coloring components consisting of FeO and Fe2O3 totalling 03 to 4.5% computed as Fe203, 0.1 to 2% Ti02 and 0.02 to 0.50% NiO, the ratio of the computed FezOa/NiO being from 5/1 to 15/1, the essential constituents totalling at least and up to 5% Z1O2.

8. A reduced, substantially neutral-colored, infrared-absorbing and ultraviolet-absorbing glass having the approximate composition 65.3% SiOz, 11.4% K20, 7% Na20, 11.1% KnO, 2% A1203, FeO and Fe2O3 totalling 2.1% computed as FezOa. 0.9% T102, and 0.21% M0.

No references cited. 

1. A REDUCED, SUBSTANTIALLY NEUTRAL-COLORED, INFRARED-ABSORBING AND ULTRAVIOLET-ABSORBING GLASS HAVING A REFRACTIVE INDEX (ND) OF ABDOUT 1.523$0.001, AN EXPANSION COEFFICIENT OF ABOUT 92 TO 98X10-7 PER *C. AND A SOFTENING POINT BETWEEN ABOUT 710* AND 735* C., AND COMPRISING ESSENTIALLY 63 TO 70% SIO2, 8 TO 19% K2O, AT LEAST ONE ALKALI METAL OXIDE IN THE INDICATED PROPORTION SELECTED FROM THE GROUP CONSISTING OF UP TO 10% NA2O AND UP TO 4% LI2O, THE PERCENTAGE OF NA2O BEING AT LEAST 4% WHEN ONLY K2O AND NA2O ARE PRESENT AND THE PERCENTAGE OF LI2O BEING AT LEAST 1% WHEN ONLY K2O AND LI2O ARE PRESENT THE SELECTED ALKALI METAL OXIDE COMPRISING LI2O WHEN THE PERCENTAGE OF K2O IS BETWEEN 16 AND 19%, THE TOTAL ALKALI METAL OXIDES BEING 15 TO 22%, AND 5 TO 17% ZNO, AND CONTAINING GLASS-COLORING COMPONENTS CONSISTING OF FEO AND FE2O3 TOTALLING 0.3 TO 4.5% COMPUTED AS FE2O3, 0.1 TO 2% TIO2, AND 0.02 TO 0.50% NIO, THE RATIO OF THE COMPUTED FE2O3/NIO BEING FROM 5/1 TO 15/1, THE ESSENTIAL CONSTITUENTS TOTALLING AT LEAST 90%. 